A typical cellular wireless network includes a number of base stations (BSs) each radiating to define a respective coverage area in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In particular, each coverage area may operate on one or more carriers each defining a respective frequency bandwidth of coverage. In turn, each base station (BS) may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a BS and may thereby communicate via the BS with various remote network entities or with other UEs served by the BS.
Further, a cellular wireless network may operate in accordance with a particular air interface protocol (radio access technology), with communications from the BSs to UEs defining a downlink or forward link and communications from the UEs to the BSs defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) and Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handover between coverage areas, and other functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may define a number of channels or specific resources for carrying signals and information between the BS and UEs. For instance, certain resources on the downlink may be reserved to carry a reference signal that UEs may detect as an indication of coverage and may measure to evaluate coverage quality, other resources on the downlink may be reserved to carry other control signaling to UEs, and still other resources on the downlink may be reserved to carry bearer traffic and other such communications to UEs. Likewise, certain resources on the uplink may be reserved to carry various control signaling from UEs to the BS, and other resources on the uplink may be reserved to carry bearer traffic and other such communications from UEs.
As UEs enter into coverage of the BS, the BS may become configured with connections to serve those UEs. For instance, for each such UE entering coverage on a particular carrier, the BS may engage in signaling with the network infrastructure to establish a bearer connection for carrying data between a gateway system and the BS, and the BS may work with the UE to establish a radio-link-layer connection for carrying data over the air between the BS and the UE on the carrier. Once so configured, the BS may then serve the UEs.
In a further aspect, BSs in a cellular wireless network can be physically arranged in various ways. For instance, BSs may be co-located with each other by having their antenna structures at largely the same geographic location (within a defined tolerance, for instance). By way of example, a single cell site could be arranged to define two BSs with separate antenna structures on a common antenna tower or other base structure. And in another example, a single physical BS that provides service separately on first and second carriers could be considered to define the two separate BSs, one operating on the first carrier and the other operating on the second carrier. Alternatively, BSs in a cellular wireless network can be distributed at some distance from each other. In particular, the antenna structure of a given BS may be located at a geographic location that is at some non-zero distance from the antenna structure of another BS.
With these arrangements, the BSs of a wireless service provider's network would ideally provide seamless coverage throughout a market area, so that UEs being served by the system could move from coverage area to coverage area without losing connectivity. In practice, however, it may not be possible to operate a sufficient number of BSs or to position the BSs in locations necessary to provide seamless coverage. As a result, there may be holes in coverage.
One way to help to resolve this problem is to operate a relay node (RN) that effectively extends the range of a BS's coverage area so as to partially or completely fill a coverage hole. Such an RN may be configured with a wireless backhaul interface for communicating with and being served by the BS, referred to as a “donor BS,” and may also be configured with a wireless access interface for communicating with and serving one or more end-user UEs, such as a cell phone, wirelessly equipped computer, tablet, and/or other device that is not set to provide wireless backhaul connectivity. For example, the RN could include a relay base station (relay-BS) that serves end-user UEs and could also include a relay-UE that is served by the donor BS and thus provides wireless backhaul connectivity for the relay-BS. In practice, the relay-BS and relay-UE could be integrated together as a single RN device or could be provided as separate devices communicatively linked together.
In this arrangement, the BS is considered to be a donor BS, in that the BS provides coverage to the relay-UE, and the relay-B S then provides coverage to one or more end-user UEs. Also, the wireless communication link between the donor BS and the relay-UE is considered to be a “relay backhaul link,” and the wireless communication link between the relay-BS and UEs served by the relay-BS is considered to be a “relay access link.” Further, to the extent the donor BS itself also serves end-user UEs, the wireless communication link between the donor BS and those UEs is considered to be a “donor access link.”
Given these arrangements, a donor BS may receive from the network data packets destined to the relay-UE and perhaps ultimately destined to one or more of the end-user UEs being served by the relay-BS (referred to herein as RN-served UEs). In particular, when a data packet arrives over the transport network for transmission to the relay-UE or to an RN-served UE, the gateway system may transmit the data packet to the donor BS over the relay-UE's or the RN-served UE's bearer connection. Then, the donor BS may transmit the data packet over a wireless backhaul connection to the relay-UE. Moreover, the relay-BS may receive the data packet from the relay-UE and may then transmit the data packet to the RN-served UE if that data packet is destined to that RN-served UE.
Additionally, a donor BS may receive data packets from an RN-served UE via the RN arrangement. In particular, the relay-BS may receive a data packet from an RN-served UE. Subsequently, the relay-UE may receive the data packet from the relay-BS and may then transmit the data packet to the donor BS over the wireless relay backhaul connection. Once the donor BS receives the data packet, the donor BS may itself process the data packet or may further transmit the data packet to another network entity, so that the wireless communication system can ultimately transmit the data packet to another UE via the network for instance.